When a President of the United States sets aside important federal lands for conservation, the accompanying fanfare typically invokes the notion of forever. But, in light of President Trump’s Executive Order 13792, maybe these national treasures should be asking our government the timeless question posed long ago by The Shirelles, Carole King, and others: “Will you still love me tomorrow?”

On April 26, 2017, President Trump signed Executive Order 13792, which directs the Secretary of the Interior, Ryan Zinke, to review and make recommendations concerning many prior presidential designations or expansions of national monuments that were made under the Antiquities Act of 1906. The Executive Order essentially suggests that some past monument designations may have been made without adequate public input, and may be overbroad or unduly restrictive of other uses of the designated lands. The Executive Order concerns monument designations or expansions since 1996, where the designation or expansion covers more than 100,000 acres or where Secretary Zinke determines it was made without adequate public outreach and coordination with stakeholders.

But the Executive Order, together with the review it requires, is probably only the first step. The review probably foreshadows a future attempt by President Trump to at least pare back certain existing national monument designations, based on Secretary Zinke’s recommendations. Prominent among the monuments that are in the cross hairs is President Obama’s controversial Bears Ears National Monument in Utah.

The Secretarial review is on a fast track. The Executive Order provides that the Secretary’s interim report is due in mid-June. The final report is due in late August, and it should include recommendations for subsequent actions. In the meantime, the Department of the Interior is inviting public comment. On May 5, 2017, it issued a press release describing the scope of and deadlines for public comment. It also listed the twenty two national monuments and five marine monuments that are subject to the ongoing review.

The Antiquities Act was enacted during the term of Theodore Roosevelt, and it empowers presidents to create national monuments with federal land to protect “historic landmarks, historic and prehistoric structures, and other objects of historic or scientific interest.” The presidential power created by the Act is unique in that it allows presidents to unilaterally protect federal land by designating national monuments. In that regard, presidential power under the Act goes beyond the often used power to issue executive orders. Presidents from Theodore Roosevelt to Barack Obama have used the power given to them under the Act.

Both presidential power to create national monuments under the Antiquities Act and Congressional power to change them under the Property Clause of the Constitution are well recognized, but President Trump’s signing of Executive Order 13792 leaves a looming question: Does a president have the power either to abolish or to reduce in size a monument designated by a previous president? The Antiquities Act is silent on that question. According to a 1938 opinion of the United States Attorney General and the legislative history of the Federal Land Policy and Management Act of 1976, the Antiquities Act does not confer upon the president the power to abolish entirely an existing national monument designation. No previous president has done so. But the administration likely will not concede the issue of whether the president can abolish a monument. Regardless of the Act, some note that the Constitution grants the president broad power to reverse actions of previous presidents. The separate question of whether a president may merely reduce the size of a monument or change its boundaries is probably a closer call than the question of complete abolition of it. Rather than abolish national monuments, President Trump might attempt to reduce the size of one or more of them.

The Act limits the size of lands that can be reserved for national monuments to “the smallest area compatible with proper care and management of the objects to be protected . . .” But that limitation can be difficult to quantify, and it has generally not stopped presidents from designating very large swaths of land as national monuments. For example, much of the public and political criticism of Bears Ears National Monument – designated by President Obama in the last month of his term – focuses on its huge size, which is about 1,350,000 acres of public land. President Clinton’s 1996 designation of Grand Staircase Escalante National Monument covers about 1.9 million acres. It has been subject to similar criticism, and it is also under review by Secretary Zinke. Although it is somewhat unusual for a president to reduce the size of an existing monument, Presidents Wilson, Truman, and Eisenhower have done so. However, these past reductions were not challenged, and so case law on the questions presented by the Executive Order is scarce. Unlike these past actions to reduce monument size, any move by President Trump to change established monuments likely will be challenged. The issues raised by his Executive Order are already highly contentious.

It remains to be seen whether any future effort by President Trump to abolish or reduce a monument’s size will withstand the inevitable legal challenge, but we can predict a few of the issues that could be raised. Of course, the prominent initial question is whether either the Antiquities Act or the Constitution’s general grant of executive authority authorizes a president to change monument designations of past presidents.

If the answer to that question is “yes,” many unresolved questions may arise about the scope of presidential authority to change designations. Can a president abolish a monument altogether? If a president can only alter, but not abolish, a monument, then by what criteria should the validity of the alteration be measured? Is the challenged reduction in size so substantial as to thwart the conservation purposes for which the monument was created? In the words of the Act, does the reduction leave the “smallest area compatible with proper care and management of the objects to be protected”? Is a paltry level of public outreach or coordination preceding a president’s designation of a monument adequate legal justification for changing the monument? Is outreach or coordination even legally relevant to a monument’s validity, and if it is, how should the adequacy of public outreach and coordination with stakeholders be tested?

Politics and public opinion will also steer the upcoming debate. The national monument issue raised by the Executive Order is a lightning rod for many, including environmental groups, Tribes, State and local governments, and those who favor limiting the reach of the federal government. This episode would not be the first time that President Trump has announced controversial policy that invites high profile legal challenges and the media attention that accompanies them.

I tend to be wary of landscape scale reservations of federal lands under the Antiquities Act and some other laws. They can be as political as they are large. Abuse of power is a concern. We always should consider whether the designation fits in size and purpose the law that is being used to authorize it. Is the designation simply a misguided, feel-good lob at a legacy, orchestrated by an outgoing president in his final days? Or is it something more substantial, with a size and purpose that are supportable under the authorizing legislation? Those are good questions for the president making the designation, for a reviewing court, and for Congress, in the rare case where it considers whether to change a designation. But, when it comes to existing national monuments, I at least question whether President Trump (and then each of his successors) should be the one who gets to decide.

Until now, national monuments have, for the most part, enjoyed an air of permanence. With some exceptions, presidents have typically deferred to the monument designations of predecessors, even while dismantling other aspects of a previous administration’s policies. But President Trump’s actions raise questions about whether the tradition might end. As legal challenges unfold, it may be years before we know to what extent this president, and every future president, could toss established national monuments into the same bin of ephemera that is used to dispose of old political appointments and presidential proclamations.

American College of Environmental Lawyers, The ACOEL, is a professionalassociation of lawyers distinguished by experience and high standards in the practice of environmental law, ethics, and the development of environmental law.